Whenever I am on Oblivion and a scout attacks me my character automatically starts running towards them and interrupting any spells I try cast on them. I don't remember it being like this on live, because on live my character would stand still while casting in offensive stance. It happens with mobs for my char too. The mob starts to melee me and my char stops the spell and starts running towards the mob.

How do I get my char to stop running towards someone automatically when they attack me? It is really annoying, because it interrupts all my spells.

This is what is happening ^^. You are attempting to run into melee combat range via auto attack which is useful on a melee toon not so much on a caster.

If Zenjah's suggestion doesn't work you can also manually turn it off in game by clicking the combat button on screen > choosing your stance (assuming ATTK stance for your mage) > clicking combat button again. This turns off the auto attack and you will not swing on a target even if in melee range but your selected stance remains until you do an action that cancels it like sitting etc. You will have to do this every time you go into / change a stance though. I prefer this method as it allows me to turn it off/on in game with only one button click and there are some select times when it it useful - see below.

BTW combat close can be useful for you also if you are on a non tracking toon such as a mage. If you have a target in target cycle but no visual on them and don't know precisely where they are. If you have combat close on then hit control-A (default for attack) and your toon will auto face the target and start running towards them. Stop them after a step or two and you now know where your target is.

Another useful fact is that anytime you take damage you will auto target whatever hit you if you have no target selected in your target window.. This was very useful for a mages back in the day because if a stealther bleed you and then re-hid simply clear your target window (left click on ground) and wait for the bleed to tick. This would auto target them (even in stealth) if they were still inside casting range giving you a moment to cast on them with a DoT. I don't know if this old trick still works as i haven't tested it since live. Good to know if you play a stealther or a caster.